1. Field of the Invention
This invention relates to electroforming and, more particularly, to a method of providing shaped electroformed parts utilizing a shrink tube initially positioned about a mandrel.
2. Description of the Prior Art
Electroforming is a process by which metal parts can be made accurately by electrochemical deposition of metal onto a mandrel. It allows parts that are relatively difficult or costly to make by standard machine shop practices to be produced economically. This plating technique provides close control of tolerances of intricate shapes and can produce smoother interior finishes of high quality.
The electroforming process has been available for many years and in general comprises four basic steps: preparation of the electroplating bath, preparation of the mandrel and its placement in the electrochemical bath, the subsequent metal buildup, and the removal of the component from the mandrel without damaging the shell of the deposited metal. Over the years, many techniques have been provided which improve on these basic steps. Examples of prior art electroforming techniques can be found in the following patents.
British Pat. No. 4499, published in 1885, describes a technique wherein the surfaces of cores are prepared to receive an electrodeposit of copper, the cores then being mounted in a depositing tank and the electrodeposition process initiated until a cylinder of deposited metal is obtained upon the core. When the deposited cylinder develops to the requisite thickness, the core with its electrodeposited cylinder is removed from the bath and cooled down, whereupon shrinkage of the core takes place and the deposited cylinder is freed from the core.
U.S. Pat. No. 1,694,962 discloses a technique for forming a layer of copper, for example, on a mandrel having a conductive layer thereon. The technique for removing the mandrel after the metal is also disclosed.
U.S. Pat. No. 3,464,898 discloses an electroforming process wherein complex hollow metal articles are formed, a conductive material being deposited on the surface of a plastic foam mandrel, a layer of metal thereafter being electrodeposited onto the conductive material and the mandrel then being separated from the metal article thus formed.
U.S. Pat. No. 3,763,030 discloses a technique for making seamless hollow cylinders by forming a cylindrical metal film on an expandable and contractable, hollow, cylindrical, rotary matrix.
U.S. Pat. No. 3,867,264 discloses an electroforming process wherein the surface contour of a master form is duplicated, a polymeric material first being applied to a master. The layer is then dried to provide a polymer layer, metal is electrolessly plated onto the polymer, metal is then electroplated to the desired thickness on the electroless plated metal layer, and thereafter the plated metal is removed from the master.
U.S. Pat. No. 3,947,348 describes a process of making a waveguide wherein copper is electrolytically deposited on a nickel steel mandrel. After plating, the assembly is heated so that the formed copper tube separates from the mandrel without sticking and thus can be taken off without exercise of undue force which would otherwise damage the mandrel or the tube.
U.S. Pat. No. 4,276,148 describes a method of making seamless hollow cylinders by electrolytically forming cylinders on a expandable and contractable mandrel. The mandrel has an inflatable outer surface or jacket which permits it to be expanded or contracted for holding or removing the electroformed cylinder therefrom.
In my prior U.S. Pat. No. 4,326,928 I disclose a method of electroforming a part wherein a metal layer is electrolessly deposited on a mandrel of heat shrinkable material, a second lyer of material is then electrodeposited over the first layer, the resultant assembly is then heated to a temperature which will shrink the mandrel, and the shrunken mandrel is removed from the electroformed part.
Additional background regarding the electroforming art is disclosed in an article entitled "Electroforming of Intricate Electronic Components", Electronics, Sept. 11, 1959, pages 114-117.
For the most part, the aforementioned electroforming processes were directed to the formation of cylindrical tubing. When parts of complex configurations are to be fabricated, the mandrels associated with such a process are usually shaped to the configuration of the part to be formed. In this situation, a method for removing the mandrel from the finished part must be provided. FIG. 8 of my aforementioned U.S. Pat. No. 4,326,528 illustrates an electroformed channel-shaped part, the shrunken mandrel inside the finished part being accessible for removal from the end of the part.
In order to make complex electroformed parts in accordance with prior art techniques, the mandrel was configured to the shape of the part as set forth hereinabove. Thus the fabrication of the mandrel itself is quite complex and costly. It is also difficult in prior art processes to metalize the inside wall of a formed part, since the mandrel is normally removed only after the part itself is removed from the plating bath.
Thus what is desired is a new electroforming process which is particularly adapted for forming parts of complex configuration, is less costly and is simpler than prior art processes and which also allows the inner wall of the formed part to be metalized while in the plating bath.